Transcript for What Would You Do: Teen boy physically and verbally abuses his girlfriend

it on purpose. Your hair looks good today. Thank you. Let me see your phone. No. I said, let me see your phone. No, why? Right now. Who are you texting? I'm not texting anyone. Reporter: An intense scene unfolding right in front of you. A young man physically and verbally abusing his teenage girlfriend. Stop giving me reasons to be mad at you. I'm -- I'm sorry. Reporter: What would you do? It's a quiet morning at Cai's cafe in metuchen, New Jersey. But above the chatter of customers and the hum of the coffee machines, this customer sees that trouble is brewing with the young couple next to him. Are you trying to mess with me or something? No. That's not okay. No, I -- Okay, don't touch me. Get off your phone. Reporter: When Nick snatches that phone away, he catches the attention of another nearby customer. Okay, I'll put it away. Hey, hey, hey. Don't touch the phone. What's wrong with you? Reporter: And now Nick tries to force grace out of the cafe. Let's go, come on. Reporter: And this man tries to stop him. Is there a problem? No, it's -- no problem here. She's just not listening to me. That's all. Reporter: But there seems to be a disagreement on how best to handle this domestic situation. You're absolutely right. There is a problem, sir, I heard it, I've identified it, but if we talk about it, it may make it worse. Reporter: Ignoring that advice, this concerned customer just won't give up. Are you okay, miss? Yeah, it was my fault, it's okay. It's nobody's fault. What's the problem? Don't handle people like that. She -- That's a young girl and she's upset. Now you've gotten all these people upset, okay? I'm really sorry. Okay, but if you're upset, don't go. Reporter: And we find out that for him, this issue hits close to home. Why do you care, why are you getting involved in this? Because my sister's been through that, that's why. And I don't put up with that. Reporter: They move to another area of the cafe, and the customer continues looking for answers and ways to help young grace. You're just a kid, right? Yeah, I'm 17. You don't need that. That's nonsense. Do you have a mom, can you call your mother? I do, but we live in the city, so, we're a little far out. Well, you can't get home? He was my ride here. Reporter: As we make our way to talk to this kind gentleman, he goes one step further. I'll give you money to get home. Oh, oh, you don't have to do that, sir. No, no, that's all right. Take the money and home. Thank you, thank you so much. Reporter: Sir, hi. I'm John Quinones. And this is part of a TV show. She's an actor, and he was an actor, too. We wanted to see how people got involved. And you were amazing. You were amazing. I know it was difficult for you to get involved? No, because I'm not going to let somebody get hurt like that. I've seen it in the past, and it's unacceptable. Reporter: So, the knee jerk reaction to immediately confront the guy may not be the best solution? It may not be if you're worried he's violent. So long as you can still control the situation, so, whatever I can do to get them to deescalate first and then we can deconstruct later. I didn't feel he was in danger yet, because she wasn't out the door yet. If she was between the door and me, my reaction would have been different. Stop it, don't touch me like that. Don't touch your phone. Reporter: When Nick storms away, this customer talks to grace, trying to get answers. Is he violent? Has he ever hit you? A few times. But I've been trying to not initiate it because I don't. What do you mean initiate it? It's not, like, your fault. That's not right. Do you need help? Reporter: Throughout the day, women also come to our young girl's aid. I don't know what's going on, I'm just telling you, you deserve better than that. Stand up for yourself and do what you feel like is right for you. Stop. Okay, I'll put it away. Are you kidding? What? She's not listening to me. I don't care. Don't touch her like that. Don't talk to her like that. It was my fault, I shouldn't of made him mad. No, it was not your fault. He's just been having a rough day. I'm just saying, this is not okay. Don't take that From any boy. Don't take From him. He's working really hard to intimidate you. Just remember that, okay? Nobody talks to you like that. Reporter: And no one comes to grace's side like this customer. Can I tell you something? You don't deserve anybody to talk to you like that, okay? It was my fault, he's just having a bad day. Reporter: Undeterred by Nick sitting just inches away, this brave woman talks directly to grace. Nothing is your fault. You are not married to him, you are not sold to him, absolutely nothing. Okay? So nobody, nobody deserves -- if your parents were here, because I'm a parent, if I saw this guy talking like this to my to talk with him. You're too young and too pretty to be with such a . He has no power over your phone, okay? Nobody, nobody should talk to you like that. She brings this upon herself. Reporter: Suddenly, another young woman steps in. She's my girlfriend, I can talk to her however I want. Did you just say you have the right to abuse your girlfriend? I'm just talking to her. It's emotional abuse. She's being sneaky and she wonders why I question her. I'm asking you to please step out of here. Right now. Take your things and leave. She's my girlfriend. If she was really your girlfriend or you really loved her or had any feelings for her, you would never talk to her like that. If anybody ever talked to me like that, and I'm married, that guy would be out of my house in a second. Okay, I -- Reporter: Even with Nick gone, this girl, just 16 years old, continues to talk to grace, trying to make her realize that she did nothing wrong. You didn't bring this on yourself. He can tell you that as many times as he wants. But you didn't bring this on yourself. You have the right to O nada privacy. You have the right to everything. You deserve happiness. Thank you. Reporter: Time to step in and talk to both ofredibly strong women. It's not right. It's not right. I am a mother, and if anybody talked to, like that to my daughter, I will kill him. Like, nobody should talk to another human being like that. Reporter: There's a lot of talk these days about men abusing women in the workplace, in Hollywood, even in the news media. Your message to young girls who are in these relationships? Leave. Get -- get out. Reporter: Why step in? It's none of your business, some people might say? People deserve happiness. And he was taking that away from her. And that wasn't okay.

This transcript has been automatically generated and may not be 100% accurate.

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